Hydraulic control for drill feeding units



Nov. 18, 1952 C. E. BRODERS HYDRAULIC CONTROL FOR DRILL FEEDING UNITS .3 Sheets-Sheet 1 Filed Jan. 11, 1950 J HJUH 5 R .E. M@ y TR.- M m a m m... .r T W A C% on O I gl/a/////-W=// NOV. 18, 1952 c, BRODERS 2,618,179

HYDRAULIC CONTROL FOR DRILL FEEDiNG UNITS Filed Jan. 11, 1950 s Sheets-Sheet 2 INVENTOR.

CLAUDE E. BRooERs 59 as 98 I Nov- 18, 1 52 c. E.BRODERS HYDRAULIC CONTROL FOR DRILL FEEDING UNITS 3 Sheets-Sheet 3 Filed Jan. 11, 1950 INVENTOR.

s R E o O R B L E D U A L C Patented Nov. 18, 1952 HYDRAULIC CONTROL FOR DRILL FEEDING UNITS Claude E. Broders, Detroit, Mich., assignor' .to

Govrc-Nelson Company, Detroit, Mich, a corporation of Michigan Application Januaryll, 195.0, Serial No. 137,992

(Cl. li -33.2)

11 claims. 1

The present invention relates to a drill feeding unit and more particularly to hydraulic controlsfor regulating the rate of feed of a drill unit. Thebroad principle of operation of the present drill feeding unit is covered in my prior United States Patents No. 2,053,514 and No. 2,426,386 and Reissue Patent No. 21,341. In the units shown in these patents, the tool feeding spindle is advanced toward the work-piece'at a feeding pressure and rate determined by the forces developed in centrifugally actuated weight" members' mounted in a conical feeding cup. An air dash pot arrangement is shown 'in'my-Patent No. 2,426,386 for cushioning the spindle feeding mechanism during the drilling operation.

In certain instances an hydraulic dash pot arrangement is desired in place of the air dash pot device previously used. However, it is impossible to secure a positive body of hydraulic fluid until the-entrapped ai r has been removed therefrom so as to provide a positive hydraulic fluid-cushion for the spindle feeding mechanism. Also, another problem concerns the accurate regulation of the rate of feed-of the spindle and the improvement of the rapid traverse feed controls.

Accordingly, it is an object ofthe present. invention to provide an hydraulic dash pot: arrangement for use-"in a drill feeding unit and in. which air and the hydraulic fluid-are separated in. the dashpot unit so that the airmay be bled from. the dash pot unit before the hydraulic cushioning action is required.

Itis another objectof the. present invention to provide control: means independent. of the-spindle feed mechanism for regulating therrat'e. of dis;- placement-of" hydraulic fluid from. the hydraulic; dash pot arrangement and. thereby to regulate more-accurately the "rate .of. feedzof the spindle.

'Itis still another obj ectof. the present. invenr tionstonprovide valtzemeans in the-:hydraulicdash. pot arrangementiof a.v drillfeeding. unit; whereby the rate of feedof the spindle-in said drillfeed ing unit. can he more. accurately regulated.v

' Itis another object oftthe :present invention. to. provide in. a .centrifugally operated; drill feeding unit aihigh and low speed. electric motor.- and controls therefor operable: to permit feeding. .of the cutting tool. when the: electric motor: iszp1- eratingiat high: speed and operable to permit the cutting toolto be returnedto-its-=normal starting position when themotor 'is'at'low'speed, and further-to-pro'vide continuous rotation of the spindle on fits return to its normal starting position-to aid'in removal -ofm;etal chips formed-by the drill-- ing operation.

iii

It is still another object of the present invention to provide an improved rapid traverse and feed control whereby the extent of rapid traverse desired of the spindle can be selectively determined and the remainder of the feed of the spindle can be controlled at a regulated rate.

Other objects of this invention will appear in.

the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings 2 Fig. 1 is a fragmentary longitudinal section of a drill feeding unit embodying the present invention.

Figs. 2, 3 and'4' are fragmentary sectional views taken on the lines 2-2, 3-1-3, and 4-4 respectively, of Fig. 1'.

Fig. 5 is a view, partly in section, taken on. the line 55 of Fig. 1.

Figs. 6 and 7 are fragmentary sectional views taken on the lines 6-6 and l-1, respectively, .of Fig. 5.

Fig. 8 is afragmentary longitudinal. sectional view showing the electric motor for operating the" present drill feeding unit.

Before explaining the present invention in detail it is to be understood that the invention. is not limited in its application to the details of construction and arrangement ofv parts illustrated in the accompanying drawings, since: the invenp tion is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology' or terminology employed herein is for the purpose of description and not of limitation.

Referring to the. drawings, a drill feeding unit is shown having arhousing Illv into which: extends a drive shaft l2 journaled in bearings forrotating a spindle feeding mechanism I4. Electric switch controls 16, which are actuated by the spindle feeding mechanism I4, are provided to regulate the operation of! an electric motor Ifl which re:- tates the drive shaft l2. The spindle feeding. mechanism. 1'4 isdrivingly connected to a spindle l8 on the end of which. is secured a collet 2 0; Formed partially by the housing 1 0 and. operably associated with the spindle feeding mechanism 14: is an hydraulic dash pot arrangement 22.

As isseen in Figure-8 of the drawings, the electric motor H con-rprises a stator-H9 and a rotor I 21 which is mounted ondrive shaft 1-2 for rotation therewith. Rigidly secured to the end 10f drive shaft I2 is a fan l 23' enclosed within the fan-shell I25. A wire outlet box I2! is provided into which extend wires (not shown) for supplying power to the electric motor H. The latter is a two speed motor for providing high and low speed rotation of said drive shaft I2, the purpose of which will be more fully explained hereafter.

Secured to one end of the stator H9 is a housing member I29 through which the drive shaft I2 extends to the spindle feed mechanism I4. A sealing means I3I is provided on drive shaft I2 to prevent passage of hydraulic fluid from within the housing I!) to the motor II. Mounted on the housing member I29 are limit switches I33 and I35 which are actuated by the switch controls I6 and I31, respectively, in response to predetermined axial movements of the spindle feeding mechanism I4.

The electric switch control I8, when actuated by the spindle feeding mechanism 14, operates to limit the stroke of the spindle I8 by regulating the speed of the motor II. The feed of the spindle I8 is stopped when the spindle feeding mechanism I4 engages a cam 24 on the long red 25. This engaging action causes the long rod 25 to pivot the bell crank 28 which in turn moves the pin 36 in a longitudinal direction to actuate the limit switch I33.

When actuated by pin 39, the limit switch I33 operates to reduce the speed of the electric motor I1 to its low speed. The spindle feeding mechanism I4, which feeds the spindle I8 by the application of centrifugal forces, is so constructed and arranged that it will not feed the spindle I8 when driven by the electric motor IT at the low speed of the latter. Instead, the spindle feeding mechanism I4 will be caused to return to its normal starting position by the action of a coil spring, later to be described.

A manually or automatically operated starting switch (not shown) is provided for increasing the speed of motor I! from its low to its high speed. If desired, this starting switch (not shown) may be operated, for example, in response to movement of a turret which holds a workpiece so that when the turret has been properly located with respect to the drill feeding unit the starting switch (not shown) will cause the speed of motor ll to be increased to its high speed and thereby to start the next drilling operation.

The other limit switch I35 is actuated by a control mechanism similar to that for limit switch I33. This mechanism includes the cam 32, short rod 34, bell crank 35 and pin 33. Limit switch I35 is provided to regulate the op eration of auxiliary equipment used in conjunction with the present drill feeding unit. For example, limit switch I35 may be adapted to control the operation of a turret which holds the workpiece whereby on return of the spindle feeding mechanism I4 to its normal starting position the turret will be actuated to move the workpiece to a new position in preparation for the next drilling operation of the drill feeding unit.

Attention is next directed to the spindle feeding mechanism I4 as illustrated in Figure 1 of the drawings. The spindle feeding mechanism I4, as here shown, is old in the art and a more detailed description thereof can be found in my prior Patents Nos. 2,054,514 and Reissue 21,341. The present spindle feeding mechanism includes a quill 46 mounted for rotation on ball bearings 42, and secured to drive shaft I2 for rotation therewith. The spindle l8 slidably fits into the quill 40 and a key 44 having fiat surfaces 45 looks spindle I8 to quill 40 for rotation therewith. A longitudinal keyway 45 is provided in quill 46 permitting axial movement of spindle II} with respect to said quill 45. Air and hydraulic fluid bleeder holes 4? are provided in the quill 4E] for a purpose which will be explained later. A conical cup 48 is keyed to spindle I3 through the longitudinal keyway 46. The conical cup 48 is rotatable with the quill 40 while it is movable longitudinally thereof to effect longitudinal movement of the said spindle I3 relative to said quill 45; A second conical cup 56 is secured to the quill 40 which is in turn connected to the drive shaft I2. The conical cups 48 and 5%! are mounted with their bases facing each other to provide an enclosed chamber of double proportions into which is loosely mounted a plurality of symmetrically disposed centrifugal weights 52. As will be readily ap parent, when the drive shaft I2 is caused to be rotated at high speeds by the electric motor I? the centrifugal weights 52 will be moved radially outwardly due to centrifugal forces and the conical cup 48, which is keyed to spindle I8 will be moved in a longitudinal direction to feed the spindle I8 to the workpiece (not shown).

In the present invention, the advancement of the spindle I8 is controlled hydraulically by a dash pot arrangement 22 including a stationary cylinder 54 formed in the housing Iii and an annular piston 56 mounted on the conical cup 48 to reciprocate and rotate within the stationary cylinder 54 and to close one end thereof. A key 58 secured in conical cup 48 extends into a 10ngitudinal keyway 53 in the annular piston 56 whereby the piston 55 will rotate with the conical cup 48.

The other end of cylinder 54 is closed by the rotating cylinder head 64 which is located within the cylinder 54 and spaced inwardly of the end seal assembly 62 and is secured to quill 4B for rotation therewith. The end seal assembly 62 prevents leakage of the hydraulic fluid from the unit and causes it to return through the return conduit 63 to the sump 68.

Seated at its opposite ends in the cylinder head 64 and the annular piston 56 is a coil spring 66, previously referred to in explaining the operation of the control switches, which biases the annular piston against the conical cup 48 and operates to return the conical cup 48 and the various parts secured thereto for axial movement therewith to their normal starting positions at the completion of each operative cycle of the feeding unit. The coil spring 66 is designed to exert an axial force against the annular piston 56 greater than that of weights 52 when the motor I1 is operated at its low speed and less than that of weights 52 when the motor is operated at its high speed. Thus, it can be seen that when the motor I! is operating at a'relatively high speed the spindle feeding mechanism I4 wil1 overcome the spring forces in coil spring 66 and will cause the spindle I8 to be fed to the workpiece, while when the motor I1 is operating at a relatively low speed the coil spring 66 will act to move the spindle feeding mechanism I4 back to its normal starting position. It is seen that this construction permits the cutting tool to continue rotating, but at a reduced rate of speed, when being removed from the workpiece. It is apparent that continuous rotation permits faster operation of the unit while at the same time providing a means of clearing the chips resulting from the cutting operation.

An hydraulic fluidor oil, for use with the dash,

The valve means I2 comprisestwo valves, the

check valve 16 and the by-pass valve IS. The checkvalve I5 includes a valve member 851 for closing valve port 84 and a valve spring 86 for: biasing the valve member 80'to a closed position. The check valve [6 operatesto prevent discharge of hydraulic fluid from cylinder 54. via conduitsv I and 14 while permitting flow from the. sump 68 to the cylinder 54 through these same conduits I0 and I4.

The. by-passvalve I8, shown in Figs. and 6 of'the drawing; includes a valve stem Blithreadedl ysecured tovalve housing 89 at 90 for axial movement inresponse to rotation of" the valve stem 88"andlocked in position by the lock nut 92. The valve stem 88 has a transverseslot 93' at its end adapted to-receive a screwdriver to'be rotated thereby. At its lower end, valve stem 88 is provided'wi'th a'longitudinal extension or cylindrical member 94' for closing the valve port 96. The lower end of the longitudinal extension or cylindrical member 94- has a transverse slot 98 for varying the effective opening of valve port 96-; It it apparent that rotation of the valve stem 05 causes axial movement of the longitudinal extension or cylindrical member 94 to vary thereby the effective opening of the transverse slot 98 at valve port 96. Thus, the rate of discharge of the hydraulic fluidfrom the cylinder 54 can be controlled by selectively rotating the valve stem 88, since the by-pass valve I8 is in a, direct pathof communication between the cylinder 54 and the sump 68'. I

This by-passvalve I8 is found to be decidedly superior in operation to the prior types of such valves. A more sensitive adjustment of the rate of flow of hydraulic fluid can be made and the transverse slot '98 does not readily become clogged. v In the prior types of by-pass valves, where the valve was cracked slightly from the valve seat-for permitting; only a limited flow of hydraulic fluid, a sensitive adjustment could not be made and the very thin, annular passage through which the fluid flowed, tended toclogvery readily causing irregularoperation of the drill feeding unit.

' Reference is now made to Figs. l4 of the drawings for an explanation of the rapid traverse means of the present invention.

In order to provide a rapid traverse for the spindle I8, a series of axially arranged bleeder ports; I100 are provided in the cylinder 54 and a valve member I02" is provided for selectively closing'said bleeder ports I00. The valve member I02 has an axial conduit I04 in communication, via, conduit IllG-and. ball check valve I01, with the. interior. of. the said housing I0. Thevalve member' I02 hasfa. plurality of ports Illl, axially and. radially spaced, enabling any of. the bleeder ports. ljflllto be selectively opened by rotation. of knurled knob I08. Also, if it is desired, all of the bleeder ports, I00 may be closed by valve member I02.

' The ball check. valve I01 in the conduit IE6 is arranged. to permitv the flow of fluids from the cylinder 54 and. to prevent the return of fluids thereto. This construction permits hydraulic fluidto be rapidly discharged from cylinder 54 during the rapid traverse portion of the feed of l s nd-l I8 wh le preventin a om being 6" drawn through conduit I06 onthe returnof the spindle I8 to its normal starting position.

In operation of the present feeding unit, the-- drive shaft I2 and the quill 40 are. caused to be.

rotated by a two speed electric motor I'I'. Asv pre viously described, when motor I! is operated at high speed the centrifugal weights 52 cause axial movement of the conical cup 48 which then causesa corresponding axial movement of the; spindle I8 and the piston member 56. Rotational movement- 'is also imparted to spindle I8 and annular piston 56 by the spindle feeding mechanism I4 through the keys 44 and 58 respectively.

When the feeding unit is in its normal startingposition shown in Fig; 1, the cylinder 54 will be substantially filled'with hydraulic fluid from the previous operating cycle-as'will be more fully described hereafter.

As the annular piston 58 advances from its normal starting position into the cylinder 55, the

hydraulic fluid therein is discharged through the lee, which has been selectively bleeder port opened, until the cylinder IQ has advanced sulficiently far to close the said open port I Until port I 05 has been closed a rapid traverse of the spindle has been provided. Thereafter, the rate of feed of spindle E8 is limitedby the rate of displacement from cylinder 54 of the hydraulic fluid therein.

Thus, after the rapid traverse portion of the been completed by contact of conical cup 13 with.

cam 24, the speed of the motor I? is reduced caus ing the spindle It to return to its normal position as explained previously, by thev spring action of spring 56.. The rate of return of the spindle; will be governed by the. rate at which the hydraulic fluid is returned to. the cylinder via the valve means 72, by suction action of. piston 56. The check valve l5 whichv is part of valve. means I2 will be opened completely by the suction action of piston 55 and thereby will, permita relatively unrestricted flow of hydraulic fluid into cylinder 54. Thus, the cylinder will be filled. with hydraulic fluid on the return. of the spindle I8 to its normal starting position and the return of the spindle will be relatively rapid.

The coil spring 55 performs two separate and distinct functions in the operation of the feeding unit. As previously described, it servesv to bias the spindle feeding mechanism I to its normal starting position shown in. Fig. l. The coil spring 66 together with annular piston 55 and cylinder head 84 also functions to separateany air that may be entrained in the .oil in the cylinder 54 during the feeding operation of the spindle. It has been found. thatthe most. satisfactory cushioning effect. of the oil isnot. achieved when any air is entrapped in the hydraulic. fluid in. the cylinder-'54. When the feeding operation. of the spindlebegins, hydraulic fluid in the-cylinder 54 will be bled out through the selectively opened port I85, and after the annular-piston. 55 has closed the selectively opened valve port- 7 I 00, the cylinder 54 will be substantially filled with hydraulic fluid. The oil which now substantially fills the cylinder 54 is being rotated by the coil spring 66, the annular piston 56 and the cylinder head 64, and due to centrifugal forces the hydraulic fluid will be thrown outwardly about the walls of the cylinder and any air which,

may be entrapped in the hydraulic fluid will accumulate about the spindle I8.

Thus, the spinning action of the coil spring 63 and the revolving piston 56 and cylinder head 64 will act to separate the entrapped air from the hydraulic fluid, and since the air is' lighter than the hydraulic fluid the air will collect about the quill 49 and spindle I8, and the slip fit be, tween said'quill 49 and said spindle l8 will permit bleeding of the air therethrough and out through holes 4i. This bleeding action will remove the air in cylinder 54 and provide a solid cushion of hydraulic fluid during the entire feeding stroke, thus permitting accurate control of the feeding operation and preventing a jump of the cutting tool at the break through point.

The present construction also provides means for varying the extent of the rapid traverse of the spindle I8 during the feeding operation. Rapid traverse of the spindle it] will occur during the feeding operation until the annular piston 55 has closed the valve port 1553 which has been selectively opened. After the piston has closed said valve port I08, the feed of the spindle It will be determined by the rate of displacement of the hydraulic fluid from the cylinder 55 as previously described. It is apparent therefore, that the operator can determine the extent of rapid feed merely by selecting the proper setting of the valve member I92.

Having thus described my invention, 1 claimi 1. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber having an open end, piston means having a normal position within said open end for closing said open end and responsive to feeding of said spindle to further enter said oil chamber, spring means in said oil chamber for biasing, said piston means toward said normal position and in opposition to feeding of said spindle, hydraulic conduit means for establishing limited communication between the oil chamber and a source of oil exterior of said oil chamber when the spindle is being fed to the workpiece and a relatively greater communication between the oil chamber and said source of oil when said spindle is being withdrawn from said workpiece, and a port in said cylindrical oil chamber in communication with the atmosphere and adapted to be closed by said piston means during the feeding of said spindle, whereby said spindle may be rapidly fed to the said workpiece when said port is open, and when said port is closed the rate of feed of said spindle is dependent on the rate of oil displacement from said oil chamber.

2. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber having an open end, piston means having a normal position closing said openend and responsive to feeding of said spindle to further enter said oil chamber, spring means for biasing said piston means toward said normal position and in opposition to feeding of said spindle, hydraulic conduit means for establishing controlled limited communication between said oil chamber and a source of oil exterior of said oil chamber when the spindle is being fed to the workpiece and a relatively greater communication between the oil chamber and said source of oil when said spindle is being withdrawn from said workpiece, whereby feeding of the spindle to the workpiece is controlled by the rate of displacement of oil from said oil chamber.

3. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried :by said housing and. adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber having an open end, piston means having a normal position within said open end for closing said open end and responsive to feeding of said spindle feeding mechanism to further enter said oil chamber, hydraulic conduit means for establishing limited communication between the oil chamber and a source of oil remote from said oil chamber when the spindle is being fed to the workpiece, axially arranged ports in said cylindrical oil chamber in communication with the atmosphere, and valve means for selectively opening one of said ports, whereby the spindle may be rapidly fed to the workpiece when one of said axially arranged ports is open and when said axially arranged ports are closed the rate of feed of said spindle is dependent on the rate of oil displacement from said oil' chamher.

4. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, a spindle feeding mechanism operable to rotate and reciprocate said spindle, and an hydraulic dash pot operably associated with said spindle feeding mechanism for regulating the rate of feed of said spindle in accordance with its rate of discharge of hydraulic fluid: valve controls for regulating the rate of flow of said hydraulic fluid comprising a check valve operable to prevent fluid flow from said dash pot while permitting fluid flow thereto, and a by-pass valve for permitting said hydraulic fluid to by-pass said check valve. 7

5. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, a spindle feeding mechanism operable to rotate and reciprocate said spindle, and an hydraulic dash pot operably associated with said spindle feeding mechanism for regulating the rate of feed of said spindle in accordance with its rate of discharge of hydraulic fluid; valve controls for regulating the rate of flow of said hydraulic fluid comprising a check valve operable to prevent fluid flow from said dash pot while permitting fluid flow thereto, and a by-pass valve for permitting said hydraulic fluid to by-pass said check valve, said by-pass valve including a cylindrical port, and a cylindrical member axially movable to close said port, said cylindrical member having a transverse slot therein whereby axial movements of said cylindrical member will vary the effective area of opening of said cylindrical port.

6. In a feeding unit for feeding a rotating tool to a workpiece and including hydraulic control means for regulating the rate of feed of said rotating tool, a by-pass valve for regulating the rate of flow of fluid through said hydraulic control means comprising a valve housing having a first and a second port communicating with the interior thereof, a valve stem in axial alignment with one of said ports, and a longitudinal extension of said valve stem having a longitudinal transverse slot therethrough and slidable into said one of said ports for varying the effective area thereof, whereby the rate of flow of said fluid through said valve ports can be regulated by axial movement of said valve stem.

'7. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber having an open end, piston means having a normal position within said open end for closing said open end and responsive to feeding of said spindle to further enter said oil chamber, a coil spring in said oil chamber for biasing said piston means toward said normal position and in opposition to feeding of said spindle, hydraulic conduit means for establishing limited communication between said oil chamber and a source of oil when said spindle is being fed to said workpiece and a relatively greater communication between said oil chamber and said source of oil when said spindle is being withdrawn from said workpiece, a port in the outer periphery of said cylindrical oil chamber in communication with the atmosphere and adapted to be closed by said piston means during the feeding of said spindle, whereby said spindle may be rapidly fed to said workpiece when said port is open and when said port is closed the rate of feed of said spindle is dependent on the rate of oil displacement from said oil chamber, and an aperture in said oil chamber along the axis thereof for bleeding air from said oil chamber during feeding of said spindle.

8. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber, piston means within said oil chamber and having a normal position at one end thereof, said piston means being responsive to feeding action of said spindle feeding mecha- 10 nism to move axially away from said normal position, hydraulic conduit means communicating with said oil chamber at the other end thereof, and an air bleeder port in said oil chamber between the ends thereof.

9. In a feeding unit for feeding a rotating tool to a workpiece including a housing, a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece, and a spindle feeding mechanism operable to rotate and reciprocate said spindle: a rapid traverse and feed control comprising a cylindrical oil chamber, piston means within said oil chamber responsive to feeding action of said spindle feeding mechanism to displace hydraulic fluid from said oil chamber whereby the rate of feed of said spindle is proportional to the rate of displacement of said hydraulic fluid, means within said oil chamber for separating air entrapped in said hydraulic fluid, and a bleeder aperture for bleeding said air from said oil chamber.

10. In a rapid traverse and feed control for use with a drill feeding unit, hydraulic control means comprising a dash pot, conduit means communicating with said dash pot and including a cylindrical portion of reduced diameter, and an axially movable cylindrical member slidably mounted in one end of said cylindrical portion, said cylindrical member having a longitudinal transverse slot whereby the effective opening at said one end or" said cylindrical portion can be varied by axial movement of said cylindrical member.

11. In a feeding unit for feeding a rotating tool to a workpiece including a housing and a rotatable and reciprocable spindle carried by said housing and adapted for feeding said tool to said workpiece: a hydraulic dash pot for regulating the rate of feed of and for providing cushioning for said spindle, means operatively associated with said spindle for rotating about the axis of said dash pot the hydraulic fluid therein, and conduit means providing communication between the exterior of said dash pot and the interior of the dash pot adjacent the axis thereof, whereby when the hydraulic fluid is rotated any entrapped air in said hydraulic fluid will be separated therefrom and may be bled from said dash pot through said conduit means.

CLAUDE E. BRODERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,069,995 Anderson Aug. 12, 1913 1,129,409 Ljungstrom Feb. 23, 1915 1,295,065 Riley et a1. Feb. 18, 1919 2,441,414 I-Iohwart et a1 May 11, 1948 

